Present day automobile engines are housed in very crowded engine compartments. With such engine compartments, even routine service on engine components is difficult. For example, to replace a spark plug, a mechanic must get a suitable tool, such as a socket wrench with extensions, past a veritable maze of accessories, cables, tubes, and hoses before he can secure the wrench about the plug. First, however, he must remove a boot supporting the ignition wire for the plug. This removal must be accomplished in spite of the fact there is scarcely room, close to the boot, for him to get his hand around the ignition wire. An obvious approach, that of pulling on the wire, is impracticable because such an approach would likely cause damage to the electrical connection at the boot, requiring replacement of the ignition wire.
There has been considerable interest in developing a tool for removing boots from spark plugs. Clark, U.S. Pat. No. 4,125,938, issued Nov. 21, 1978, discloses such a tool which can be fitted over a spark plug boot and which has jaws with lip-like protrusions for engaging the end of the boot directed towards the base of the spark plug. Opening like a scissor, the handles of Clark's tool extend laterally a substantial distance while the open jaws of the tool are being slid over the boot. Uncluttered space located perpendicularly to the centerline of the tool must be provided. The lateral extension of this required space is of the same order of magnitude as the length of the tool, limiting its usefulness. Clark's tool is best suited to those situations in which the spark plug boot is only a relatively short distance beyond the reach of the mechanic's unaided hand.
Hansen, U.S. Pat. No. 4,202,088, issued May 13, 1980, discloses a spark plug boot puller with no moving parts and hence no scissor-type action. To use Hansen's tool, a mechanic slips a shoulder of its L-shaped member beneath one side of the end of the boot directed towards the base of the spark plug and then pulls the boot from the plug. At most only about one-half of said end of the boot actually contacts the shoulder. Moreover, to use this tool, one must have a substantial amount of uncluttered space. This uncluttered space must not only extend the length of the boot but also have a transverse width greater than that of the puller. In addition, the mechanic must have room in which he can exert a side force pushing the shoulder laterally and under the boot. Otherwise, the tool, which lacks any means for providing this necessary side force, could not be properly positioned beneath the boot.
Simmons, U.S. Pat. No. 4,425,697, issued Jan. 17, 1984, discloses a spark plug boot remover having an inwardly extending lip which is similar to the shoulder of the L-shaped member in Hansen's tool. Both this lip and Hansen's shoulder must be slipped beneath the end of the boot facing towards the base of the spark plug. Simmon's tool has essentially the same space and side force requirements for placement of the inwardly extending lip beneath said end of the boot as does the placement of the shoulder in Hansen's tool. Simmon's tool differs from Hansen's tool in that the former also includes means for pulling the boot off of the spark plug by pushing downwardly on a lever which in turn pushes an arm of the tool against the head of the engine forcing the boot puller away from the head of the engine, thereby facilitating removal of the boot.